The present invention pertains to a method and a device for producing cases with rounded corners in a book case machine.
Cases with rounded corners have no sharp-edged corners and exhibit an improved resistance to wear. They are used, e.g., for photo albums, diaries, writing cases and children's books. The cover boards of such cases have rounded corners, over which the cloth cover that is punched out in a star-shaped fashion on the corners is stretched and then pressed on. The specific star shape that is responsible for the production of clean turn-ins on the corners depends on the radius of the subsequent rounding, the cloth material and the thickness of the case. Neither excessive material accumulations nor visible gaps can be created.
DE 41 29 241 A1 discloses a method and a device for turning and gluing cloths over the borders of the cover board in the corner regions. The overhangs of the cloth are punched out in a tongue-shaped fashion in the region of the rounded corners and initially uprighted as well as pressed on the end faces of the lateral borders. These overhangs are then turned over and ultimately pressed on the up side of the cover board. For this purpose, the turn-in tool for rounded corners is provided with a guide surface that is adapted to the contour of the rounded corners, wherein a straight edge is provided above the guide surface which positions the overhanging strips upright in an aligned fashion during the upward movement of the tool. During this turning-over, the moving direction extends linearly from the lateral borders toward the center of the case, namely at an angle of 45° relative to the longitudinal side and the broadside of the case. In DE 41 29 241 A1, the corners are turned in during a separate production step after the lateral turn-in and the turn-in at the head/foot.
In the book case machine BDM 20 R of the firm Hörauf, a turn-in device of this type for rounded corners is arranged in an additional processing station situated upstream of the lateral turn-in station and the station for the turn-in at the head/foot, wherein a calibrating station is arranged downstream of the three turn-in stations in order to subsequently shape the rounded corners. The constructive expenditure for the two additional stations and for the expanded transport system that serves for the cyclic transport into the successively arranged processing stations is quite significant. In addition, the required floor space for the machine is increased.